Managing held telephone calls at the call-forwarding system

ABSTRACT

A method and an apparatus are disclosed that manage the held calls for an off-premises terminal at the system that extends calls to the terminal, such as a private branch exchange or other type of data-processing system, instead of at the system that is receiving the extended calls, such as a mobile switching center at which a cell phone is registered. The disclosed technique is based on the observation that the extending system knows of an incoming call to an off-premises terminal before the receiving system. As a result, the extending system can advantageously select the calls that it holds versus the calls that it sends to the receiving system. The extending system can control the routing costs and provide a consistent look-and-feel of call control to the off-premises terminal user.

FIELD OF THE INVENTION

The present invention relates to telecommunications in general, and,more particularly, to the handling of one or more held calls, such as ina call-waiting or three-way call scenario.

BACKGROUND OF THE INVENTION

FIG. 1 depicts a schematic diagram of a telecommunications system in theprior art. Telecommunications system 100 comprises:

i. telecommunications network 101,

ii. private branch exchange 102,

iii. on-premises telecommunications terminals 103 and 104,

iv. data-processing system 108,

v. off-premises telecommunications terminal 109, and

vi. network telecommunications terminals 111 and 112,

all of which are interconnected as shown.

Telecommunications network 101 comprises the Public Switched TelephoneNetwork, which is a complex of telecommunications equipment that isowned and operated by different entities throughout the World. In theUnited States of America, for example, the Public Switched TelephoneNetwork (or “PSTN”) comprises an address space that is defined by tendigits, and, therefore, comprises 10 billion unique addresses or“telephone numbers.” The public switched telephone networks in othercountries are similar.

Network 101 interconnects other telecommunications networks, whichinclude: (i) the cellular network supported by data-processing system108 and (ii) the enterprise network supported by private branch exchange102. The cellular network supported by system 108 providestelecommunications service to one or more cellular telecommunicationsterminals, including terminal 109. The enterprise network supported byexchange 102 provides telecommunications service to one or moretelecommunications terminals, for example terminals 103 and 104, withinthe enterprise area served, such as an office building or campus.

Additionally, network 101 provides telecommunications service totelecommunications terminals that are in the Public Switched TelephoneNetwork, such as terminals 111 and 112. The telecommunications terminalsthat network 101 serves might be wireline terminals or wirelessterminals, or a combination of both.

Data-processing system 108 is a mobile switching center that providesservice for cellular phones (e.g., terminal 109, etc.) that areregistered with system 108. Alternatively, data-processing system 108might be a different type of data-processing system than a mobileswitching center, such as a wireline switch, a packet router, and soforth. Similarly, terminal 109 might be a different type of terminalthan a cellular phone.

Private branch exchange (PBX) 102 is capable of switching incoming calls(e.g., from terminal 111, etc.) from the Public Switched TelephoneNetwork of network 101 via communications paths in trunk group 120(e.g., path 120-1, path 120-2, etc.) to one or more on-premisesterminals, such as on-premises terminals 103 and 104. Private branchexchange 102 is also capable of handling outgoing calls from one or moreon-premises terminals to the Public Switched Telephone Network via thecommunications paths that make up trunk group 120.

Private branch exchange 102 is also capable of forwarding an incomingcall, such as from terminal 111, to an “off-premises” terminal, such asterminal 109, that is affiliated with exchange 102 and accessiblethrough network 101. This type of forwarding to a terminal affiliatedwith exchange 102 is also known as “extending” a call because theconnection to the off-premises terminal appears to exchange 102 as anadditional PBX line. Exchange 102 extends the call to the off-premisesterminal in addition to switching the same incoming call to an“on-premises terminal” within the enterprise area that exchange 102serves. Terminals 103 and 104 are considered to be on-premises terminalswith respect to private branch exchange 102, while terminal 109 isconsidered to be an off-premises terminal with respect to exchange 102.Note that in telecommunications system 100, terminals 111 and 112 arenot considered to be off-premises terminals because, unlike terminal109, they are not affiliated with exchange 102.

To accomplish (i) the switching of an incoming, enterprise-related callto an on-premises terminal and (ii) the extending of the call to thecorrect off-premises terminal, private branch exchange 102 maintains atable that correlates the off-premises telephone number to theon-premises, private branch exchange extension. Table 1 depicts a tablethat illustrates the correlation. TABLE 1 PBX Extension-to-PSTN NumberDatabase On-Premises Telecommunications Private BranchTelecommunications Terminal Exchange Extension Network Number 103732-555-0102, x11 201-555-1236 104 732-555-0102, x12 908-555-3381 . . .. . . . . .

As an example, a first caller at terminal 111 who wishes to reach thePBX user of terminal 103 dials the PBX number (i.e., 732-555-0102).Private branch exchange 102 receives the incoming call and the extensionnumber (i.e., x11) as specified by the caller. By using storedinformation that is similar to the information in Table 1, privatebranch exchange 102 determines that the call is also to be extended tooff-premises telephone number 201-555-1236. This is the telephone numberthat is associated with off-premises terminal 109, which belongs to thePBX user of terminal 103. Exchange 102 then extends the call to terminal109 via an available resource, communications path 120-1. The ideabehind transmitting the call to both terminal 103 and 109 (or sometimesto terminal 109 only) is that if the PBX user is not reachable at hisoffice phone (i.e., terminal 103), then possibly he is reachable at aphone that is outside of the office (i.e., terminal 109). The extendingof the call to an off-premises terminal enhances the caller's experienceby only requiring the caller to use a single telephone number to reachthe PBX user, regardless of whether or not the PBX user is in theoffice.

Continuing with the example, a second caller at terminal 112, who alsowishes to reach the PBX user of terminal 103, dials the same PBX numberas the first caller (i.e., 732-555-0102). Private branch exchange 102receives the second incoming call and the extension number (i.e., x11)as specified by the second caller, and determines that the second callis also to be extended to off-premises telephone number 201-555-1236,associated with terminal 109. Exchange 102 then extends the second callto terminal 109 via the next available resource, communications path120-2.

At this point in the example, data-processing system 108 is handling twocalls for terminal 109 on two separate communications paths from privatebranch exchange 102. If terminal 109 terminates only a single PBX line,also known as a “call appearance,” data-processing system 108 isresponsible for holding the waiting, second call until the user ofterminal 109 signals (i.e., “flashes”) data-processing system 108 to:(i) put the first call on hold, and (ii) connect the second call to theterminal.

SUMMARY OF THE INVENTION

There are disadvantages for a data-processing system, such as a mobileswitching center or central office, to manage the held calls for atelecommunications terminal to which a private branch exchange extendscalls. One disadvantage is in cost. It costs more to allocate multiplecommunications paths between the extending private branch exchange andthe data-processing system that is local to the terminal than it wouldcost to allocate a single path. Another disadvantage is in the userinterface. The overall feature functionality that the user of theoff-premises terminal is able to access is distributed across theextending private branch exchange and the data-processing system.Therefore, the combined user interface to both systems looks and feelsinconsistent to the terminal's user.

The present invention provides a technique to manage the held calls foran off-premises terminal at the system that extends calls to theterminal, such as a private branch exchange or other type ofdata-processing system, instead of at the system that is receiving theextended calls, such as a mobile switching center at which a cell phoneis registered. The technique is based on the observation that theextending system knows of an incoming call to an off-premises terminalbefore the receiving system. As a result, the extending system canadvantageously select the calls that it holds versus the calls that itsends to the receiving system. The extending system can control therouting costs by being able to control the number of communicationspaths that are allocated for a particular off-premises terminal. Inaddition, relocating the control of calls to the extending systemprovides a consistent look-and-feel of call control to the off-premisesterminal user who is already using other features that are based in theextending system.

The techniques in the illustrative embodiment are applicable to callsthat are held, regardless of where those calls originate from. As afirst example, a first call might originate from a terminal that is notassociated with the private branch exchange; in this case, the privatebranch exchange notifies the off-premises terminal of the call waiting,instead of the receiving data-processing system notifying the terminal.As a second example, a second call that is routed through the privatebranch exchange might originate from the off-premises terminal itself;later on, the private branch exchange, rather than the data-processingsystem, might swap a held call intended for the off-premises terminalinto the communications path that was allocated when the off-premisesterminal originated the second call.

A private branch exchange, which is one type of data-processing system,is the call-forwarding system in the illustrative embodiment. As thosewho are skilled in the art will appreciate, the techniques that aretaught in this disclosure can be implemented alternatively in anothertype of data-processing system (e.g., a central office switch, a packetrouter, etc.).

For pedagogical purposes, this disclosure focuses primarily on a systemin which the off-premises terminal terminates a single call appearance.It will be clear to those who are skilled in the art, after reading thisdisclosure, how to make and use a telecommunication system in which theterminal terminates multiple call appearances. In the disclosedtechnique, M calls can be concurrently handled by the private branchexchange in the illustrative embodiment for an off-premises extensionthat terminates N call appearances, wherein M and N are positiveintegers, M is greater than or equal to N, and (M−N) is equal to thenumber of held (or waiting) calls at the private branch exchange.

The illustrative embodiment of the present invention comprises:receiving a second call for a telecommunications terminal that isengaged in a first call, wherein the first call is established via afirst communications path between a private branch exchange telephonesystem and the telecommunications terminal through the Public SwitchedTelephone Network; and putting the first call on hold at the privatebranch exchange telephone system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a schematic diagram of telecommunications system 100 inthe prior art.

FIG. 2 depicts a first schematic diagram of telecommunications system200 that comprises private branch exchange telephone system 202, inaccordance with the illustrative embodiment of the present invention.

FIG. 3 depicts a block diagram of the salient components of privatebranch exchange 202, in accordance with the illustrative embodiment ofthe present invention.

FIG. 4 depicts a flowchart of the salient tasks associated with privatebranch exchange 202 handling one or more held calls that are associatedwith telecommunications terminal 209.

FIG. 5 depicts a second schematic diagram of telecommunications system200, in accordance with the illustrative embodiment of the presentinvention.

DETAILED DESCRIPTION

FIG. 2 depicts a schematic diagram of a telecommunications system, inaccordance with the illustrative embodiment of the present invention.Telecommunications system 200 comprises:

i. telecommunications network 201,

ii. private branch exchange telephone system 202,

iii. on-premises telecommunications terminals 203 and 204,

iv. data-processing system 208,

v. off-premises telecommunications terminal 209, and

vi. network telecommunications terminals 211, 212, and 213,

all of which are interconnected as shown.

Telecommunications network 201 comprises the Public Switched TelephoneNetwork (PSTN), in accordance with the illustrative embodiment. ThroughPublic Switched Telephone Network infrastructure, as well as throughother switching and transmission infrastructure, network 201 providestelecommunications service to telecommunications terminals such asterminals 211, 212, and 213.

Network 201 also interconnects multiple telecommunications networks.Those networks include: (i) the enterprise network that private branchexchange 202 supports and (ii) the cellular network that data-processingsystem 208, a mobile switching center, supports. The enterprise networksupported by private branch exchange 202 provides telecommunicationsservice to one or more on-premises telecommunications terminals,including terminals 203 and 204. The cellular network supported bydata-processing system 208 provides telecommunications service to one ormore cellular telecommunications terminals, including terminal 209.

FIG. 2 also depicts multiple telecommunications terminals of varioustypes. Those terminal types include Plain Old Telephone Service (POTS)terminals, as exemplified by terminal 211; office desksets, asexemplified by terminals 203 and 204; cell phones, as exemplified byterminal 209; and so forth. As those who are skilled in the art willappreciate, the present invention is also applicable to othercombinations of terminals than what FIG. 2 depicts.

Private branch exchange 202 is a data-processing system, the salientcomponents of which are described below and with respect to FIG. 3.Private branch exchange 202 is capable of switching incoming calls(e.g., from terminal 211, etc.) from the Public Switched TelephoneNetwork via one or more communications paths in trunk group 220 toon-premises terminals, such as terminals 203 and 204. Exchange 202 isalso capable of handling outgoing calls from on-premises terminals tothe Public Switched Telephone Network via one or more communicationspaths in trunk group 220.

Private branch exchange 202 is also capable of forwarding an incomingcall to a terminal other than the terminal at the called telephonenumber. Specifically, exchange 202 is capable of extending an incomingcall (e.g., from terminal 211, etc.) to a telephone number of an“off-premises” terminal. From exchange 202's perspective, an“off-premises” terminal is one that is accessible through the PublicSwitched Telephone Network (e.g., via communications path 220-1, etc.),while still being affiliated with exchange 202 as an extension to theenterprise network supported by exchange 202. Exchange 202 is capable ofextending the incoming call to the off-premises terminal in addition to(or independently of) switching the same incoming call to an on-premisesterminal within the enterprise area (e.g., an office building, etc.)that is served by exchange 202. For pedagogical purposes, terminal 209is an off-premises terminal in telecommunications system 200.

Private branch exchange 202 is connected to telecommunications systemsthat are present in network 201 via ISDN trunks, as are known in theart. Each communications path 220-i, wherein i is a value greater thanzero and less than or equal to the number of trunks in trunk group 220,comprises an ISDN trunk in accordance with the illustrative embodiment.As those who are skilled in the art will appreciate, in some alternativeembodiments, exchange 202 might have additional trunk groups thandepicted in FIG. 2. Moreover, as those who are skilled in the art willappreciate, exchange 202 might be connected to network 201 via othertypes of communications paths. For example, exchange 202 might receiveat least some of the incoming calls via the Session Initiation Protocolover an Internet Protocol-based network.

It will be clear to those skilled in the art, after reading thisdisclosure, how to make and use alternative embodiments of the presentinvention in which private branch exchange 202 providestelecommunications service to a different number of on-premisesterminals and to a different number off-premises terminals than thosedepicted.

Private branch exchange 202 is also capable of performing the tasksdescribed below and with respect to FIG. 4, in accordance with theillustrative embodiment. It will be clear to those skilled in the art,after reading this disclosure, how to make and use private branchexchange 202. Moreover, as those who are skilled in the art willappreciate, there can be alternative embodiments of the presentinvention in which, for example, a switch or another type ofdata-processing system (i.e., other than the private branch exchangetelephone system in the illustrative embodiment) performs the describedtasks. The data processing systems in those alternative embodimentsinter-operate with the Public Switched Telephone Network thatconstitutes network 201, with another type of network (e.g., an InternetProtocol-based network, a wireless network, etc.), and so forth. Puttingit differently, the present invention is equally well suited forimplementation in public and private telecommunications systems, and inwireline and wireless systems as well.

Data-processing system 208, a mobile switching center, is capable ofswitching incoming calls from the Public Switched Telephone Network viaone or more communications paths to cellular terminals, such as terminal209. Data-processing system 208 is also capable of handling outgoingcalls from cellular terminals to the Public Switched Telephone Networkvia one or more communications paths. System 208 communicates withterminal 209 via one or more radio base stations, in well-known fashion.It will be clear to those skilled in the art how to make and usedata-processing system 208.

In accordance with the illustrative embodiment of the present invention,data-processing system 208 is a mobile switching center and off-premisesterminal 209 is a cell phone. As those who are skilled in the art willappreciate, in some alternative embodiments, data-processing system 208might be a different type of data-processing system, such as a wirelineswitch, a packet router, and so forth. Correspondingly, off-premisesterminal 209 might be, in those alternative embodiments, a differenttype of terminal, such as a wireline deskset, a softphone, and so forth.

For pedagogical purposes, this disclosure focuses primarily on a systemin which telecommunications terminal 209 terminates a single callappearance, as represented by communications path 221-1. As will bedescribed below and with respect to FIGS. 4 and 5, however, someoff-premises terminals in some variations of the illustrative embodimentterminate multiple call appearances.

FIG. 3 depicts a block diagram of the salient components of privatebranch exchange 202 in accordance with the illustrative embodiment ofthe present invention. Private branch exchange 202 comprises: switchingfabric 301, processor 302, and memory 303, interconnected as shown.

Switching fabric 301 is capable of performing all of the tasks describedbelow and with respect to FIG. 4 under the direction of processor 302.It will be clear to those skilled in the art, after reading thisdisclosure, how to make and use switching fabric 301.

Processor 302 is a general-purpose processor that is capable ofreceiving called-related data from switching fabric 301, of reading datafrom and writing data to memory 303, and of executing the tasksdescribed below and with respect to FIG. 4. In some alternativeembodiments of the present invention, processor 302 might be aspecial-purpose processor. In either case, it will be clear to thoseskilled in the art, after reading this disclosure, how to make and useprocessor 302.

Memory 303 is a non-volatile random-access memory that stores theinstructions and data used by processor 302. Memory 303 stores the PBXon-premises extension and affiliated off-premises telephone number foreach PBX user, which are shown in Table 1. It will be clear to thoseskilled in the art, after reading this disclosure, how to make and usememory 303.

FIG. 4 depicts a flowchart of the salient tasks associated with privatebranch exchange 202 handling one or more held calls that are associatedwith telecommunications terminal 209, in accordance with theillustrative embodiment of the present invention. It will be clear tothose skilled in the art which tasks depicted in FIG. 4 can be performedsimultaneously or in a different order than that depicted.

At task 401, private branch exchange 202 checks if a call is arriving.If a call is arriving, task execution proceeds to task 402. If not, taskexecution proceeds to task 407.

At task 402, exchange 202 receives, in well-known fashion, an incomingcall that is associated with off-premises terminal 209. As an example,the called telephone number of the incoming call might map to one ormore terminals that include off-premises terminal 209. As anotherexample, the incoming call might originate from off-premises terminal209 and be intended for another terminal (e.g., terminal 203, terminal211, etc.).

At task 403, exchange 202 determines whether or not all call appearancesthat terminate at terminal 209 are already in use. If all callappearances that terminate at terminal 209 are already in use, taskexecution proceeds to task 405. If not, task execution proceeds to task404.

At task 404, exchange 202 establishes the call on an idle callappearance. For example, if the incoming call is intended for terminal209, exchange 202 extends the call to terminal 209 using an idle callappearance. Task execution then proceeds to task 401.

At task 405, exchange 202 holds the arrived call in well-known fashion.As those who are skilled in the art will appreciate, exchange 202 mightcontinue to transmit a ringing tone to the calling party or mightprovide some other type of feedback or information to the calling party.

At task 406, exchange 202 notifies the intended terminal of the arrivedcall that is being held. For example, if terminal 209 is the calledterminal, exchange 202 transmits a call-waiting indication in well-knownfashion.

At task 407, exchange 202 checks if it is receiving a signal fromoff-premises terminal 209 to hold an active call. If it is receiving thesignal, task execution proceeds to task 408. If not, task executionproceeds to task 401.

At task 408, exchange 202 holds the active call in well-known fashion.This has the effect of freeing up a call appearance at terminal 209.

At task 409, optionally, exchange 202 connects a held call to terminal209 by using an idle call appearance. Alternatively, the user ofterminal 209 can use the idle call appearance to originate a new call.Task execution then proceeds to task 401.

In a first example that illustrates some of the described tasks, a userof private branch exchange 202, who is a technical supportrepresentative, is available to accept calls from customers. The PBXuser is at his cell phone, off-premises terminal 209, which has a singlecall appearance.

Private branch exchange 202 receives an incoming first call from a firstcustomer. The customer is using his home phone, network terminal 211, tocall for technical support. The customer calls a first telephone number(i.e., the called telephone number), “1-800-555-TECH,” which isassociated with private branch exchange 202 and, as a result, routesthrough network 201 to exchange 202. Exchange 202 determines that thecall is to be extended to terminal 209, which is at a second telephonenumber, “973-555-1324.” Exchange 202 extends the call to terminal 209.

A second customer calls into private branch exchange 202 (i.e., calls“1-800-555-TECH”) for technical support. Exchange 202 receives theincoming second call and determines, in well-known fashion, that thesecond call should also be extended to the tech support rep at terminal209. However, because the only call appearance of terminal 209 isalready in use (i.e., there are no available call appearances), exchange202 holds the incoming second call and notifies terminal 209 (i.e., the“intended” terminal) of the call that is waiting. Exchange 202 mightnotify terminal 209 by a “call waiting” tone, or provide calleridentification information to terminal 209, or do both.

Private branch exchange 202 then receives a signal from terminal 209, inwhich the signal indicates that terminal 209's user wishes to put thefirst call on hold. The user specifies the hold by selecting a functionthat results in terminal 209 generating a signal that exchange 202, inturn, recognizes as a hold command (but which is not detectable bydata-processing system 208). Exchange 202 puts the first call (i.e., theactive call) on hold in response to having received the signal. Exchange202 then connects the held, second call to terminal 209 on thenow-available call appearance.

In a second example that illustrates some of the described tasks, a userof private branch exchange 202, who is a technical supportrepresentative, is available to accept calls from customers. The PBXuser is at his cell phone, off-premises terminal 209, which has a singlecall appearance. The tech support rep is already engaged in a first callat terminal 209, wherein the first call has been established throughprivate branch exchange 202. Exchange 202 might have extended the callto the tech support rep's terminal, or the tech support rep might haveinitiated the call by calling back a particular customer (i.e., atterminal 211) through exchange 202.

The PBX user of off-premises terminal 209 then wishes to call a subjectmatter expert for the purpose of conferencing the expert onto the call.However, since the only call appearance of terminal 209 is already inuse for the first call, the user has to signal exchange 202 to put thefirst call on hold. The user specifies the hold by selecting a functionthat results in terminal 209 generating a signal that exchange 202, inturn, recognizes as a hold command. The user then makes the second callto the subject matter expert.

Private branch exchange 202 receives the signal from terminal 209, inwhich the signal indicates that terminal 209's user wishes to put thefirst call on hold. Exchange 202 puts the first call (i.e., the activecall) on hold in response to having received the signal. Exchange 202then receives the second call from terminal 209, and routes the callthrough to the called party at her branch office phone, terminal 212.

Meanwhile, exchange 202 continues to receive additional calls, in whichterminal 209 is the intended receiving terminal for at least some of thecalls. Each time, exchange 202 transmits a call-waiting indication toterminal 209, which provides information about each caller to the userof terminal 209. Each call for which an idle call appearance is notavailable is held at private branch exchange 202, as opposed todata-processing system 208.

Private branch exchange 202 then receives a second signal from terminal209 that specifies to conference in the subject matter expert of thesecond call. The user specifies the conferencing in by selecting afunction that results in terminal 209 generating a signal that exchange202, in turn, recognizes as a conference command (but which is notdetectable by data-processing system 208). Exchange 202 then joins thesecond call to the first call as part of a three-way call.

A third example that illustrates some of the described tasks is depictedin FIG. 5 and involves off-premises terminal 509, which terminates twocall appearances instead of only one appearance. Terminal 509 issupported by data-processing system 508, which is also capable ofhandling two call appearances per terminal. It will be clear to thoseskilled in the art how to make and use system 508 and terminal 509. Inthe example, a user of private branch exchange 202, who is a technicalsupport representative, has already signaled for exchange 202 to put afirst call that involves a first customer on hold. Also, exchange 202has already connected a second call that involves a second customer whois using terminal 212 to communicate; the second call has been connectedto terminal 509 via a first communications path.

The PBX user is at his home phone, off-premises terminal 509, which isserved by system 508, a central office switch. The user is able totoggle between the two call appearances within his phone. The first callappearance is enabled by communications path 220-1 and 221-1. The secondcall appearance is enabled by communications path 220-2 and 221-2.

Meanwhile, terminal 509 is also engaged in a third call with a thirdcustomer that exchange 202 has established on the second communicationspath. The user of terminal 509, however, wishes to talk with the firstcustomer (on the held first call) and indicates this to exchange 202.Private branch exchange 202 then receives a signal from terminal 509, inwhich the signal indicates that terminal 509's user wishes to put thethird call on hold. The user specifies the hold by selecting a functionthat results in terminal 509 generating a signal that exchange 202, inturn, recognizes as a hold command. Exchange 202 puts the specifiedactive call on hold in response to having received the signal. Exchange202 then connects the held first call to terminal 509 on thenow-available call appearance enabled by the second communications path.

It is to be understood that the above-described embodiments are merelyillustrative of the present invention and that many variations of theabove-described embodiments can be devised by those skilled in the artwithout departing from the scope of the invention. For example, in thisSpecification, numerous specific details are provided in order toprovide a thorough description and understanding of the illustrativeembodiments of the present invention. Those skilled in the art willrecognize, however, that the invention can be practiced without one ormore of those details, or with other methods, materials, components,etc.

Furthermore, in some instances, well-known structures, materials, oroperations are not shown or described in detail to avoid obscuringaspects of the illustrative embodiments. It is understood that thevarious embodiments shown in the Figures are illustrative, and are notnecessarily drawn to scale. Reference throughout the specification to“one embodiment” or “an embodiment” or “some embodiments” means that aparticular feature, structure, material, or characteristic described inconnection with the embodiment(s) is included in at least one embodimentof the present invention, but not necessarily all embodiments.Consequently, the appearances of the phrase “in one embodiment,” “in anembodiment,” or “in some embodiments” in various places throughout theSpecification are not necessarily all referring to the same embodiment.Furthermore, the particular features, structures, materials, orcharacteristics can be combined in any suitable manner in one or moreembodiments. It is therefore intended that such variations be includedwithin the scope of the following claims and their equivalents.

1. A method comprising: receiving a second call for a telecommunicationsterminal that is engaged in a first call, wherein said first call isestablished via a first communications path between a private branchexchange telephone system and said telecommunications terminal throughthe Public Switched Telephone Network; and putting said first call onhold at said private branch exchange telephone system.
 2. The method ofclaim 1 wherein the putting of said first call on hold is in response toa signal that is received from said telecommunications terminal afterthe receiving of said second call.
 3. The method of claim 1 furthercomprising connecting said second call to said telecommunicationsterminal via said first communications path after the putting of saidfirst call on hold.
 4. The method of claim 1 wherein the telephonenumber of said telecommunications terminal is coupled with a firsttelephone number that exists within the address space of said privatebranch exchange telephone system.
 5. The method of claim 1 wherein saidcommunications path comprises an Integrated Services Digital Networktrunk that is connected to said private branch exchange telephonesystem.
 6. The method of claim 1 wherein said telecommunicationsterminal is also engaged in a third call that is established on a secondcommunications path between said private branch exchange telephonesystem and said telecommunications terminal through the Public SwitchedTelephone Network.
 7. The method of claim 6 further comprising: puttingsaid third call on hold at said private branch exchange telephonesystem; and connecting said first call to said telecommunicationsterminal via said second communications path.
 8. The method of claim 1wherein said second call is received via the Session InitiationProtocol.
 9. The method of claim 1 further comprising transmitting, fromsaid private branch exchange telephone system, a notification of saidsecond call to said telecommunications terminal.
 10. A methodcomprising: extending, from a private branch exchange telephone system,a first call to a telecommunications terminal at a second telephonenumber that is associated with a data-processing system, wherein thecalled number of said first call is a first telephone number that isassociated with said private branch exchange telephone system; receivinga second call while said first call is in progress, wherein the callednumber of said second call is also said first telephone number; andtransmitting, from said private branch exchange telephone system andthrough said data-processing system, a notification of said second callto said telecommunications terminal.
 11. The method of claim 10 furthercomprising: extending, from a private branch exchange telephone system,a third call to said telecommunications terminal; wherein said secondcall is received while said third call is also in progress.
 12. Themethod of claim 11 wherein the called number of said third call is alsosaid first telephone number.
 13. The method of claim 10 wherein saidnotification comprises a call-waiting indication.
 14. The method ofclaim 10 wherein said second call is received via the Session InitiationProtocol.
 15. The method of claim 10 wherein said first call is extendedto said telecommunications terminal via a communications path thatcomprises an Integrated Services Digital Network trunk that is connectedto said private branch exchange telephone system.
 16. A methodcomprising: (a) establishing, through a first data-processing system, afirst call in which a telecommunications terminal is engaged, whereinthe telephone number of said telecommunications terminal is associatedwith a second data-processing system that is physically distinct fromsaid first data-processing system; (b) receiving a second call whilesaid first call is in progress, wherein said telecommunications terminalis a part of said second call as one of: (i) the originating terminal ofsaid second call, and (ii) the intended receiving terminal of saidsecond call; and (c) holding said second call at said firstdata-processing system.
 17. The method of claim 16 further comprising:(d) establishing, through said first data-processing system, a thirdcall in which said telecommunications terminal is engaged; wherein saidsecond call is received while said third call is also in progress. 18.The method of claim 17 further comprising: (e) receiving a fourth callwhile said first and third calls are in progress, wherein saidtelecommunications terminal is a part of said fourth call as one of: (i)the originating terminal of said second call, and (ii) the intendedreceiving terminal of said second call;
 19. The method of claim 18further comprising (f) holding said fourth call at said firstdata-processing system.
 20. The method of claim 16 further comprising(d) transmitting, from said first data-processing system, a notificationof said second call to said telecommunications terminal.
 21. The methodof claim 16 wherein a Session Initiation Protocol-basedtelecommunications terminal is also engaged in said call.
 22. The methodof claim 16 further comprising: (d) joining, at said firstdata-processing system, said second call to said first call.